US5331209A - Auto-reset circuit with improved testability - Google Patents

Auto-reset circuit with improved testability Download PDF

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US5331209A
US5331209A US08/023,674 US2367493A US5331209A US 5331209 A US5331209 A US 5331209A US 2367493 A US2367493 A US 2367493A US 5331209 A US5331209 A US 5331209A
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terminal
coupled
power
mosfet
active element
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Yoshimitu Fujisawa
Yasuhiro Shin
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Lapis Semiconductor Co Ltd
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Oki Electric Industry Co Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/22—Modifications for ensuring a predetermined initial state when the supply voltage has been applied
    • H03K17/223—Modifications for ensuring a predetermined initial state when the supply voltage has been applied in field-effect transistor switches
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/30—Modifications for providing a predetermined threshold before switching
    • H03K17/302—Modifications for providing a predetermined threshold before switching in field-effect transistor switches

Definitions

  • This invention relates to an auto-reset circuit used to initialize an electronic circuit when the electronic circuit is powered up, or when its power supply is momentarily interrupted.
  • LSI large-scale-integrated
  • a disadvantage of this simple auto-reset circuit is that it fails to produce a reset signal if the supply voltage rises slowly in comparison to the resistor-capacitor time constant, or if power is interrupted for an interval that is brief in relation to that time constant.
  • the one that comes closest to the present invention has a p-channel metal-oxide-semiconductor field-effect transistor (referred to below as a P-MOSFET) and a resistor coupled in series between the power-supply terminals, the source of the P-MOSFET being coupled to V DD and its drain to the resistor.
  • An n-channel metal-oxide-semiconductor field-effect transistor (referred to below as an N-MOSFET) and another resistor are also coupled in series between the power-supply terminals, the source of the N-MOSFET transistor being coupled to V SS and its drain to the resistor.
  • the gates of both the P-MOSFET and N-MOSFET are coupled to the drain of the P-MOSFET.
  • the reset signal is output from the drain of the N-MOSFET.
  • This circuit produces a reset signal that is initially high, but goes low when the supply voltage reaches a value equal to the sum of the threshold voltages of the two MOSFETs.
  • the reset signal is typically output while the supply voltage rises from zero to about 1.4 V, then released as the supply voltage rises from 1.4 V to a steady-state 5 V.
  • tests may be performed at a reduced supply voltage such as 2.4 V.
  • the auto-reset circuit may fail to release the reset signal, causing the device to be rejected as defective. To allow a reasonable margin in such tests, the auto-reset circuit needs to release the reset signal at about 1.9 V.
  • Yet another problem of the above auto-reset circuit is that in some cases it may generate a reset signal with an inadequate pulse width, or fail to output a reset signal at all. This problem occurs not only at power-up, but also when the supply voltage drops momentarily during operation, then recovers. It occurs particularly when the supply voltage rises rapidly (in a few hundred nanoseconds, for example), and the reset signal must drive a significant capacitive load.
  • the internal reset signal does drive a significant capacitive load, because there are many internal circuits to be reset. If the reset signal is routed to those circuits directly, the capacitance of the signal-line wiring is large. If buffers are used, the reset signal must drive the input capacitance of the buffers. A capacitive load on the order of half a picofarad is typical. If the resistor through which the reset signal is output has sufficient resistance to hold current flow through the auto-reset circuit to about ten microamperes during the steady state, and the power supply rises to five volts in a few hundred nanoseconds, then the reset signal will be released while the capacitive load is still charging and the reset signal is still inactive.
  • Another object of the invention is to ensure that an adequate reset signal is generated even if the power-supply potential rises rapidly.
  • Yet another object of the invention is to ensure that a reset signal is output when the power supply is interrupted, even if the interruption is momentary.
  • Still another object of the invention is to avoid needlessly high current drain during operation.
  • a further object of the invention is to enable current drain through the auto-reset circuit to be reduced to zero for testing purposes.
  • An auto-reset circuit comprises first and second power-supply terminals for receiving two different power-supply potentials, an output terminal for output of a reset signal, a first active element, and a second active element.
  • the first active element has three terminals, the third terminal controlling conduction between the first and second terminals.
  • the first terminal is coupled to the first power-supply terminal
  • the second terminal is coupled through a resistor to the second power-supply terminal
  • the third terminal is coupled directly to the second power-supply terminal.
  • the second active element similarly has three terminals, the third terminal controlling conduction between the first and second terminals.
  • the first terminal is coupled to the second power-supply terminal
  • the second terminal is coupled to the output terminal and through a resistor to the first power-supply terminal
  • the third terminal is coupled to the second terminal of the first active element.
  • This first aspect of the invention assures release of the reset signal even at low power-supply voltages.
  • An auto-reset circuit has the same structure except that the third terminal of the first active element is coupled to a control signal input terminal, instead of to the second power-supply terminal.
  • the control signal enables the first active element to be turned off, thereby stopping current flow during tests.
  • An auto-reset circuit has the same structure except that the third terminal of the first active element is coupled to the second terminal of the first active element.
  • a resistor is inserted between the second terminal of the first active element and the third terminal of the second active element, and a capacitor is coupled between the third terminal of the second active element and the second power-supply terminal, to delay the release of the reset signal.
  • first, second, and third aspects of the invention can be combined in various ways and further features can be provided, including a diode to discharge the capacitor and a logic gate to control output of the reset signal during tests.
  • the invented circuit can be fabricated as a complimentary metal-oxide-semiconductor (CMOS) circuit in which the first and second active elements are MOSFETs and their first, second, and third terminals are their source, drain, and gate, respectively.
  • CMOS complimentary metal-oxide-semiconductor
  • FIG. 1 is a circuit diagram of an auto-reset circuit illustrating a first embodiment of the invention.
  • FIG. 2 is a voltage waveform diagram illustrating the operation of FIG. 1.
  • FIG. 3 is a circuit diagram of an auto-reset circuit illustrating a second embodiment of the invention.
  • FIG. 4 is a voltage waveform diagram illustrating the operation of FIG. 3.
  • FIG. 5 is a circuit diagram of an auto-reset circuit illustrating a third embodiment of the invention.
  • FIG. 6 is a voltage waveform diagram illustrating the operation of FIG. 5.
  • FIG. 7 is a circuit diagram of an auto-reset circuit illustrating a fourth embodiment of the invention.
  • FIG. 8 is a voltage waveform diagram illustrating the operation of FIG. 7.
  • FIG. 9 is a circuit diagram of an auto-reset circuit illustrating a fifth embodiment of the invention.
  • FIG. 10 is a voltage waveform diagram illustrating the operation of FIG. 9.
  • FIG. 11 is another voltage waveform diagram illustrating the operation of FIG. 9.
  • FIG. 12 is a circuit diagram of an auto-reset circuit illustrating a sixth embodiment of the invention.
  • FIG. 13 is a voltage waveform diagram illustrating the operation of FIG. 12.
  • FIG. 14 is another voltage waveform diagram illustrating the operation of FIG. 12.
  • FIG. 15 is a circuit diagram of an auto-reset circuit illustrating a seventh embodiment of the invention.
  • FIG. 16 is a voltage waveform diagram illustrating the operation of FIG. 15.
  • FIG. 17 is another voltage waveform diagram illustrating the operation of FIG. 15.
  • FIG. 18 is a circuit diagram of an auto-reset circuit illustrating a eighth embodiment of the invention.
  • FIG. 19 is a voltage waveform diagram illustrating the operation of FIG. 18.
  • FIG. 20 is another voltage waveform diagram illustrating the operation of FIG. 18.
  • FIG. 21 is a circuit diagram of an auto-reset circuit illustrating a ninth embodiment of the invention.
  • FIG. 22 is a voltage waveform diagram illustrating the operation of FIG. 21.
  • FIG. 23 is another voltage waveform diagram illustrating the operation of FIG. 21.
  • FIG. 24 is a circuit diagram of an auto-reset circuit illustrating a tenth embodiment of the invention.
  • FIG. 25 is a voltage waveform diagram illustrating the operation of FIG. 24.
  • FIG. 26 is another voltage waveform diagram illustrating the operation of FIG. 24.
  • FIG. 27 is a circuit diagram of an auto-reset circuit illustrating a eleventh embodiment of the invention.
  • FIG. 28 is a voltage waveform diagram illustrating the operation of FIG. 27.
  • FIG. 29 is another voltage waveform diagram illustrating the operation of FIG. 27.
  • FIG. 30 is a circuit diagram of an auto-reset circuit illustrating a twelfth embodiment of the invention.
  • FIG. 31 is a voltage waveform diagram illustrating the operation of FIG. 30.
  • FIG. 32 is another voltage waveform diagram illustrating the operation of FIG. 30.
  • FIG. 33 is a circuit diagram of an auto-reset circuit illustrating a thirteenth embodiment of the invention.
  • FIG. 34 is a circuit diagram of an auto-reset circuit illustrating a fourteenth embodiment of the invention.
  • FIG. 35 is a circuit diagram of an auto-reset circuit illustrating a fifteenth embodiment of the invention.
  • FIG. 36 is a circuit diagram of an auto-reset circuit illustrating a sixteenth embodiment of the invention.
  • FIG. 37 is a circuit diagram of an auto-reset circuit illustrating a seventeenth embodiment of the invention.
  • FIG. 38 is a circuit diagram of an auto-reset circuit illustrating a eighteenth embodiment of the invention.
  • FIG. 39 is a circuit diagram of an auto-reset circuit illustrating a nineteenth embodiment of the invention.
  • FIG. 40 is a circuit diagram of an auto-reset circuit illustrating a twentieth embodiment of the invention.
  • FIG. 41 is a circuit diagram of an auto-reset circuit illustrating a twenty-first embodiment of the invention.
  • FIG. 42 is a circuit diagram of an auto-reset circuit illustrating a twenty-second embodiment of the invention.
  • FIG. 43 is a circuit diagram of an auto-reset circuit illustrating a twenty-third embodiment of the invention.
  • FIG. 44 is a circuit diagram of an auto-reset circuit illustrating a twenty-fourth embodiment of the invention.
  • FIG. 45 is a circuit diagram of an auto-reset circuit illustrating a twenty-fifth embodiment of the invention.
  • FIG. 46 is a voltage waveform diagram illustrating the operation of FIG. 45.
  • FIG. 47 is another voltage waveform diagram illustrating the operation of FIG. 45.
  • FIG. 48 is a circuit diagram of an auto-reset circuit illustrating a twenty-sixth embodiment of the invention.
  • FIG. 49 is a voltage waveform diagram illustrating the operation of FIG. 48.
  • FIG. 50 is another voltage waveform diagram illustrating the operation of FIG. 48.
  • FIG. 51 is a voltage waveform diagram of a momentary power loss in FIG. 45.
  • FIG. 52 is a voltage waveform diagram of a momentary power loss in FIG. 48.
  • FIG. 53 is a circuit diagram of an auto-reset circuit illustrating a twenty-seventh embodiment of the invention.
  • FIG. 54 is a voltage waveform diagram illustrating the operation of FIG. 53.
  • FIG. 55 is another voltage waveform diagram illustrating the operation of FIG. 53.
  • FIG. 56 is a circuit diagram of an auto-reset circuit illustrating a twenty-eighth embodiment of the invention.
  • FIG. 57 is a voltage waveform diagram illustrating the operation of FIG. 56.
  • FIG. 58 is another voltage waveform diagram illustrating the operation of FIG. 56.
  • FIG. 59 is a circuit diagram of an auto-reset circuit illustrating a twenty-ninth embodiment of the invention.
  • FIG. 60 is a voltage waveform diagram illustrating the operation of FIG. 59.
  • FIG. 61 is a circuit diagram of an auto-reset circuit illustrating a thirtieth embodiment of the invention.
  • FIG. 62 is a voltage waveform diagram illustrating the operation of FIG. 61.
  • FIG. 63 is a circuit diagram of an auto-reset circuit illustrating a thirty-first embodiment of the invention.
  • FIG. 64 is a voltage waveform diagram illustrating the operation of FIG. 63.
  • FIG. 65 is a circuit diagram of an auto-reset circuit illustrating a thirty-second embodiment of the invention.
  • FIG. 66 is a circuit diagram of an auto-reset circuit illustrating a thirty-third embodiment of the invention.
  • FIG. 67 is a circuit diagram of an auto-reset circuit illustrating a thirty-fourth embodiment of the invention.
  • FIG. 68 is a voltage waveform diagram illustrating the operation of FIG. 67.
  • FIG. 69 is a circuit diagram of an auto-reset circuit illustrating a thirty-fifth embodiment of the invention.
  • FIG. 70 is a voltage waveform diagram illustrating the operation of FIG. 69.
  • FIG. 71 is a circuit diagram of an auto-reset circuit illustrating a thirty-sixth embodiment of the invention.
  • FIG. 72 is a voltage waveform diagram illustrating the operation of FIG. 71.
  • FIG. 73 is a circuit diagram of an auto-reset circuit illustrating a thirty-seventh embodiment of the invention.
  • FIG. 74 is a circuit diagram of an auto-reset circuit illustrating a thirty-eighth embodiment of the invention.
  • FIG. 75 is a circuit diagram of an auto-reset circuit illustrating a thirty-ninth embodiment of the invention.
  • FIG. 76 is a voltage waveform diagram illustrating the operation of FIG. 75.
  • FIG. 77 is a circuit diagram of an auto-reset circuit illustrating a fortieth embodiment of the invention.
  • FIG. 78 is a circuit diagram of an auto-reset circuit illustrating a forty-first embodiment of the invention.
  • FIG. 79 is a circuit diagram of an auto-reset circuit illustrating a forty-second embodiment of the invention.
  • FIG. 80 is a voltage waveform diagram illustrating the operation of FIG. 79.
  • FIG. 81 is a circuit diagram of an auto-reset circuit illustrating a forty-third embodiment of the invention.
  • FIG. 82 is a circuit diagram of an auto-reset circuit illustrating a forty-fourth embodiment of the invention.
  • V TN and V TP will be used to denote N-MOSFET and P-MOSFET threshold voltages, respectively, the threshold voltage of a MOSFET being the absolute gate-source voltage at which the MOSFET turns on. Typically, V TN and V TP are about 0.7 V. It will be assumed that during normal, steady-state operation the supply voltage V DD -V SS exceeds the threshold voltages V TN and V TP sufficiently to enable the MOSFETs to turn on "hard;” that is, with negligible on-resistance.
  • FIG. 1 is a circuit diagram of an auto-reset circuit illustrating a first embodiment of the present invention.
  • This auto-reset circuit has a first power-supply input terminal 31 to which V DD is applied, a second power-supply input terminal 32 to which V SS is applied, and an outputterminal 33, the potential at which is denoted V O .
  • the reset signal RS is output at the output terminal 33.
  • the circuit comprises a first three-terminal active element 41, a second three-terminal active element 42, and two resistors 51 and 52.
  • the first active element 41 is a P-MOSFET.
  • the second active element 42 is an N-MOSFET.
  • the circuit is thus a CMOS circuit.
  • P-MOSFET 41 and resistor 51 are coupled in series between the two power-supply terminals: the source of P-MOSFET 41 is coupled to the first power-supply terminal 31, the drain of P-MOSFET 41 is coupled to one terminal of resistor 51, and the other terminal of resistor 51 is coupled to the second power-supply terminal 32.
  • the gate of P-MOSFET 41 is also coupled to the second power-supply terminal 32; this is a novel feature ofthe present invention.
  • V DD is applied not only to the source of P-MOSFET 41 but also to the substrate or well in which P-MOSFET 41 is formed, as indicated by the conventional symbol in the drawing; that is, P-MOSFET 41 has no back-gate bias.
  • N-MOSFET 42 and resistor 42 are likewise coupled in series between the two power-supply terminals: one terminal of resistor 52 is coupled to the first power-supply terminal 31, the other terminal of resistor 52 is coupled to the drain of N-MOSFET 42, and the source of N-MOSFET 42 is coupled to the second power-supply terminal 32.
  • the output terminal 33 is coupled to the drain of N-MOSFET 42.
  • the gate of N-MOSFET 42 is coupled tothe drain of P-MOSFET 41.
  • the gate potential of N-MOSFET 42 is denoted by the symbol V G .
  • N-MOSFET 42 also has no back-gate bias; its source is at the same potential (V SS ) as the well or substrate in which it is formed.
  • V TP of P-MOSFET 41 andV TN of N-MOSFET 41 are shown as slightly unequal: for example, V TP is 0.7 V and V TN 0.8 V. This is not a necessary condition; the invention is also applicable to circuits with equal threshold voltages.
  • V DD , V G , and V O are all at the same potential as V SS .
  • V DD is shown rising in relation to V SS .
  • the supply voltage V DD -V SS is initially less than the threshold voltage V TP of P-MOSFET 41, so P-MOSFET 41 is off.
  • N-MOSFET 42 is also off, because its gate is pulled down through resistor 51 to V SS .
  • the output terminal 33 is therefore pulled up through resistor 52 to V DD , and the output voltage V O rises together with V DD .
  • V G -V SS passes V TN and N-MOSFET 42 turns on.
  • N-MOSFET 42 and resistor 42 now act as a voltage divider between V DD and V SS , but as the gate potential V G of N-MOSFET 42 continues to rise, the on-resistance of N-MOSFET 42 quickly decreases in comparison with the resistance of resistor 52, and the drain potential of N-MOSFET 42approaches V SS .
  • the output voltage V O at output terminal 33 accordingly falls back toward V SS .
  • V O is shown as falling to V SS instantaneously, but the fall actually takes place over a certain span of time within interval D.
  • RS is an active-high reset signal that canbe used to initialize the internal circuits of an LSI or other device at power-up.
  • the reset signal RS is released when the supply voltage V DD -V SS equals the threshold voltage V TN of N-MOSFET 42 plus the voltage drop acrossP-MOSFET 41.
  • this voltage drop was V TP .
  • the voltage drop can be made arbitrarily small by increasing the resistancevalue of resistor 51. If the resistance of resistor 51 is high enough that the voltage drop across P-MOSFET 41 is substantially nil, then the reset signal RS will release when the supply voltage V DD -V SS equals the larger of V TP and V TN .
  • FIG. 3 is a circuit diagram of an auto-reset circuit illustrating a second embodiment of the invention. Elements identical to elements of the first embodiment shown in FIG. 1 have the same reference numerals.
  • V SS is applied to the first power-supply terminal 31 and V DD is applied to the second power-supply terminal 32.
  • the first active element is therefore an N-MOSFET 61 instead of the P-MOSFET 41 in FIG. 1
  • the second active element is a P-MOSFET 62 instead of the N-MOSFET 42 in FIG. 1.
  • the active elements and resistors are interconnected in the same manner as in FIG. 1.
  • FIG. 4 is a voltage waveform diagram illustrating the operation of the second embodiment.
  • V DD when power is turned on V DD is shown as remaining constant while V SS decreases. This may appear different from FIG. 2, but in fact the two drawings show the same power-upevent.
  • V DD and V SS do not have independent absolute values; only the difference between them is meaningful.
  • V G now denotes the gate potential of P-MOSFET 62.
  • V G and V O are shown in relation to V DD .
  • V SS , V G , and V O are all equal to V DD .
  • V SS decreases in intervals B and C the gate-source voltage
  • E the supply voltage V DD -V SS is in its steady state and the output voltage V O remains at V DD .
  • the reset signal in this second embodiment is active low: it normally staysat the high level (V DD ), but goes low (V SS ) for an interval during power-up.
  • V DD high level
  • V SS low
  • the choice between the first and second embodiments depends on whether an active-high or an active-low reset signal is more convenient.
  • FIG. 5 is a circuit diagram of an auto-reset circuit illustrating a third embodiment of the invention. Elements identical to elements of the first embodiment shown in FIG. 1 have the same reference numerals.
  • this embodiment operates like the first embodiment except that the gate potential V G of N-MOSFET 42 is now divided by the resistance ratio of resistors 51 and 53, so V G rises at a more moderate rate than V DD . Since it takes V G longer to reach the threshold voltage V TN of N-MOSFET 42, interval C is longer than in FIG. 2, and when V G does reach V TN , the V DD potential is higher than in FIG. 2. The potential V O of the reset signal RS therefore follows V DD to a higher level before dropping back to V SS .
  • the supply-voltage value at which N-MOSFET 42 turns on and reset signal RS is released can be adjusted by altering the resistance ratio of resistors 51 and 53. If resistors 51 and 53 have substantially equal resistance values (both 500 kilohms, for example) and the on-resistance of P-MOSFET 41 is negligible in comparison, then RS will release at about 1.6 V instead of the 0.8 V mentioned in the first embodiment.
  • the release voltage can be increased by increasing the value of resistor 53 in relation to resistor 51, or decreased by decreasing the value of resistor 53 in relation to resistor 51, as required by the application.
  • FIG. 7 is a circuit diagram of an auto-reset circuit illustrating a fourth embodiment of the invention. Elements identical to elements of the second embodiment shown in FIG. 3 have the same reference numerals.
  • This fourth embodiment is related to the second embodiment in the same way that the third embodiment was related to the first. Specifically, an additional resistor 53 is inserted in series between resistor 51 and the drain of N-MOSFET 61, and the gate of P-MOSFET 62 is coupled to a point between resistors 51 and 53.
  • this embodiment operates like the second embodiment except that the gate potential V G of P-MOSFET 62, being divided by resistors 51 and 53, falls at a more moderate rate. As a result, interval C is longer than in FIG. 4, and the reset signal RS follows V SS down to a lower level before returning to the V DD level.
  • the supply-voltage value at which the reset signal RS is released can be adjusted by altering the resistance ratio of resistors 51 and 53. Increasing the resistance of resistor 53 in relation to resistor 51 makes RS release at a higher supply voltage value (a lower V SS level in FIG. 8). Decreasing the resistance of resistor 53 in relation to resistor 51 makes RS release at a lower supply voltage value (a higher V SS level in FIG. 8).
  • the first four embodiments solve the problem of failure of the reset signalto release, and the third and fourth embodiments enable the release point to be set at any desired level between the higher of the two transistor threshold voltages V TP and V TN and the steady-state supply voltage. These embodiments do not, however, solve the other problems referred to in the prior art. If the power supply rises quickly (in a matter of microseconds or less, for example) the reset signal RS may have inadequate duration, or may not be output at all. Modifications of the above embodiments to solve this problem will be described in the next fourembodiments.
  • FIG. 9 is a circuit diagram of an auto-reset circuit illustrating a fifth embodiment of the invention. Elements identical to elements of the first embodiment shown in FIG. 1 have the same reference numerals.
  • a third resistor 54 is inserted in series between the gate of N-MOSFET 42 (the second active element) and the drain of P-MOSFET 41 (the first active element).
  • the gate of N-MOSFET 42 is furthermore coupled through a capacitor 71 to the second power-supply terminal 32.
  • the capacitor 71 is connected to a point between the gate of N-MOSFET 42 and resistor 54.
  • V G is now not only the gate potential ofN-MOSFET 42 but also the potential to which capacitor 71 is charged in relation to V SS .
  • FIG. 10 is a voltage waveform diagram illustrating the case in which V DD rises slowly in comparison to the time constant of resistor 54 and capacitor 71. As it rises in interval C, V DD charges capacitor 71through resistor 54; that is, V DD is integrated by resistor 54 and capacitor 71 to produce the gate potential V G . Since V DD rises slowly, however, integration is able to keep pace, and V G has substantially the same waveform as in FIG. 2.
  • the reset signal RS also hassubstantially the same waveform (V O ) as in FIG. 2.
  • FIG. 11 is a voltage waveform diagram illustrating the case in which V DD rises quickly in comparison to the time constant of resistor 54 and capacitor 71.
  • FIG. 11 would apply, for example, if resistor 54 has a resistance of 500 kilohms, capacitor 71 has a capacitance of about 12 picofarads (making the time constant 6 microseconds), and V DD rises in about 1 microsecond.
  • interval A in FIG. 11 before power-up V DD , V G , and V O are all at the same potential as V SS .
  • interval B When power is turned on, there is a very brief interval B during which V DD is less than the threshold voltage V TP of P-MOSFET 41, and both P-MOSFET 41 and N-MOSFET 42 are off. In interval B the reset output voltage V O beginsto rise together with V DD , as in FIG. 10.
  • V DD rises all the way to the steady state, quickly passing both transistor threshold levels V TP and V TN .
  • P-MOSFET therefore 41 turns on and V DD begins to charge capacitor 71 through resistor 54.
  • the gate potential V G has the waveform of V DD integrated by resistor 54 and capacitor 72. Because of the time constant of resistor 54 and capacitor 72, the rise of V G takes place at a comparatively moderate rate over intervals F, G, and H.
  • V G -V SS remains less than the threshold voltage V TN , so N-MOSFET 42 remains off and the output voltage V O continues to follow V DD .
  • V G -V SS passes V TN , N-MOSFET 42 turns on and the output voltage V O falls back to the V SS level.
  • Interval I shows the steady state, in which V G is at substantially the same potential as V DD , N-MOSFET 42 is turned on hard, and V O is held reliably at the V SS level.
  • the reset signal RS would have a pulse width of only about 17 nanoseconds.
  • resistor 54 and capacitor 71 assuming the above-mentioned values of 500 kilohms for resistor 54 and 12 picofarads for capacitor 71, the pulse width becomes approximately 1.1 microseconds, making the reset much more dependable. If this pulse width is still inadequate it can be increased by increasing theresistance of resistor 54 or the capacitance of capacitor 71, or both. Accordingly, the fifth embodiment enables a reliable power-up reset to be carried out even with a fast-rising power supply.
  • FIG. 12 is a circuit diagram of an auto-reset circuit illustrating a sixth embodiment of the invention. Elements identical to elements of the fifth embodiment shown in FIG. 9 have the same reference numerals.
  • the sixth embodiment has the same circuit topology as the fifth embodiment,but V SS is applied to the first power-supply terminal 31, V DD is applied to the second power-supply terminal 32, the first active element is an N-MOSFET 61, and the second active element is a P-MOSFET 62.
  • V SS is applied to the first power-supply terminal 31
  • V DD is applied to the second power-supply terminal 32
  • the first active element is an N-MOSFET 61
  • the second active element is a P-MOSFET 62.
  • FIG. 13 is a voltage waveform diagram illustrating the case in which the fall of V SS (that is, the rise of V DD ) is slow in relation to the time constant of resistor 54 and capacitor 71. Since capacitor 71 has adequate time to charge during the fall of V SS , the waveforms in FIG.13 are substantially the same as those of the second embodiment in FIG. 4.
  • FIG. 14 is a voltage waveform diagram illustrating the case in which the fall of V SS is quick in relation to the time constant of resistor 54 and capacitor 71.
  • the waveforms in FIG. 14 are identical to those in FIG. 11 with the roles of V DD and V SS and the positive and negative senses of the waveforms reversed. Due to the presence of resistor 54 and capacitor 71, an active-low reset pulse with an adequate pulse width is obtained despite the rapid transition of the supply voltage from zero volts to its steady state.
  • the sixth embodiment provides the same effects as the fifth embodiment, except that the reset signal RS is active low.
  • FIG. 15 is a circuit diagram of an auto-reset circuit illustrating a seventh embodiment of the invention. Elements identical to elements of thefifth embodiment shown in FIG. 9 have the same reference numerals.
  • resistor 53 inserted in series between resistor 51 and the drain of P-MOSFET 41, as in the third embodiment.
  • Resistor 54 is coupled to a point between resistors 51 and 53.
  • FIG. 16 is a voltage waveform diagram illustrating the operation of the seventh embodiment when the rise of V DD is slow in relation to the time constant of resistors 53 and 54 and capacitor 71. Since capacitor 71 has ample time to charge during the rise of V DD , the waveforms are substantially the same as in FIG. 6, which illustrated the third embodiment. V G rises somewhat more slowly, however, because the gate capacitance of N-MOSFET 42 must be charged through both resistor 53 and resistor 54. Consequently, the reset signal RS attains a higher potential V O than in FIG. 6.
  • FIG. 17 is a voltage waveform diagram illustrating the operation of the seventh embodiment when V DD rises quickly in relation to the time constant of resistors 53 and 54 and capacitor 71.
  • the waveforms are similar to those of the fifth embodiment in FIG. 11, except that V G rises even more slowly, since capacitor 71 must be charged through both resistors 53 and 54 instead of just resistor 54.
  • the pulse width of the reset signal is therefore even greater than in FIG. 11.
  • the seventh embodiment combines the advantages of the third and fifth embodiments: when V DD rises slowly, the V DD level at which the reset signal RS is released can be adjusted by adjusting the resistance ratio of resistors 51 and 53; and when V DD rises fast, an adequate reset pulse width can be obtained by suitable selection of the values of resistors 51 and 53 and capacitor 71.
  • FIG. 18 is a circuit diagram of an auto-reset circuit illustrating an eighth embodiment of the invention. Elements identical to elements of the sixth embodiment shown in FIG. 12 have the same reference numerals.
  • the eighth embodiment is related to the sixth in the same way that the seventh was related to the fifth, by the addition of a resistor 53 coupledin series between resistor 51 and the first active element, which in the sixth and eighth embodiments is the N-MOSFET 61.
  • the operation of the eighth embodiment will be explained briefly with reference to FIGS. 19 and20.
  • FIG. 19 is a voltage waveform diagram illustrating the case in which the fall of V SS (that is, the rise of V DD ) is slow in relation to the time constant of resistors 53 and 54 and capacitor 71.
  • FIG. 20 is a voltage waveform diagram illustrating the case in which V SS falls quickly in relation to this time constant. These two diagrams are identical to FIGS. 16 and 17 with the roles of V DD and V SS and the positive and negative senses of the waveforms reversed.
  • the eighth embodiment provides the same effects as the seventh, except that the resetsignal RS is active low.
  • the fifth through eighth embodiments solve the reset problem presented by afast-rising power supply at power-up. They do not, however, solve the problem of a momentary power interruption followed by a quick recovery. Indeed, if the interruption is sufficiently short and the recovery sufficiently quick, no reset signal will be output at all, because capacitor 71 will not have time to discharge and the second active element(N-MOSFET 42 or P-MOSFET 62) will remain on.
  • FIG. 21 is a circuit diagram of an auto-reset circuit illustrating a ninth embodiment of the invention. Elements identical to elements of the fifth embodiment shown in FIG. 9 have the same reference numerals.
  • This embodiment has been obtained from the fifth embodiment by coupling thegate of N-MOSFET 42 (the second active element) to the first power-supply terminal 31 through a diode 72.
  • the anode of diode 72 is connected to a point between the gate of N-MOSFET 42 and resistor 54.
  • the cathode of diode 72 is connected to a point between resistor 52 and the first power-supply terminal 31.
  • V G is now not only the gate potential of N-MOSFET 42 and the potential of the charge in capacitor 72, but also the anode potential of diode 72.
  • FIG. 22 is a voltage waveform diagram illustrating the operation when V DD rises slowly at power-up, later drops due to a momentary power interruption, then rises slowly again, “slowly” meaning slowly in relationto the time constant of resistor 54 and capacitor 71.
  • the cathode potential (V DD ) of diode 72 is equal to or higher than the anode potential (V G ), so diode 72 does not conduct.
  • V G anode potential
  • V DD has fallen far enough that the difference between V G and V DD equals or exceeds the forward voltage (0.7 V,for example) necessary to make diode 72 conduct.
  • Diode 72 now offers littleresistance, and capacitor 71 begins to discharge rapidly through diode 72 to the first power supply terminal 31.
  • V G begins to drop sharply, paralleling the drop of V DD .
  • V DD falls below the threshold voltage V TP of P-MOSFET 41, which turns off, but capacitor 71 continues discharging through diode 72.
  • V G -V SS falls below the threshold voltage V TN of N-MOSFET 42 and N-MOSFET 42 turns off.
  • the reset output voltage V O therefore rises to V DD , but since V DD is by now approaching V SS , the resulting reset pulse is small and of brief duration.
  • V DD has fallen all the way to V SS , so V O also returns to V SS .
  • V DD remains at V SS and V G falls below the threshold voltage of diode 72.
  • the forward voltage across diode 72 is now insufficient for substantial conduction to take place.
  • Capacitor 71 continues to discharge, at a slower rate, through resistors 54 and 51 to the second power supply terminal 32. If resistors 51 and 54 have resistances of 500 kilohms and capacitor 71 has a capacitance of 3 picofarads, then in about 3.8 microseconds during this interval V G decreases from 0.7 V to 0.2 V, at which level N-MOSFET 42 is turned off hard.
  • V DD exceeds the threshold voltage V TP of P-MOSFET 41, so P-MOSFET 41 turns on, capacitor 71 begins to charge again, and V G now rises.
  • V G -V SS is still less than the threshold voltage V TN of N-MOSFET 42, so N-MOSFET 42 remains off and the outputvoltage V O continues to rise together with V DD .
  • diode 72 By permitting capacitor 71 to discharge quickly in intervals K, L, and M, diode 72 allows N-MOSFET 42 to turn off even during a relatively brief power interruption, so that a reset signal can be output when power is recovered.
  • the voltage waveform (V O ) of the reset signal during recovery from the power interruption in intervals O and P is substantiallythe same as the waveform in intervals B and C at power-up.
  • FIG. 23 shows the case in which the supply voltage rises quickly in relation to the time constant of resistor 54 and capacitor 71, both at power-up and in recovering from a momentary power interruption.
  • the waveforms in intervals A, B, F, G, H, and I at power-up are the same as the waveforms of the fifth embodiment, illustrated in FIG. 11.
  • the waveforms in intervals J, K, L, M, and N, during which V DD drops momentarily to V SS are the same as in FIG. 22.
  • the waveforms during recovery from the power interruption in intervals O, P, Q, S, and T are generally similar to the waveforms in intervals B, F, G, H, and I at power-up.
  • the main difference is that, since V G startsrising from a value slightly higher than V SS , it reaches the thresholdvoltage V TN of N-MOSFET 42 at the beginning of interval Q instead of the end, so the reset pulse is shorter by the width of interval Q than at power-up.
  • the reduction in pulse width is comparatively slight, however.
  • resistor 54 and capacitor 71 permit an adequate reset pulse to be output even when the power supply rises quickly, and as in FIG.
  • diode 72 enables a reset signal to be output after even a momentary power interruption.
  • FIG. 24 is a circuit diagram of an auto-reset circuit illustrating a tenth embodiment of the invention. Elements identical to elements of the ninth embodiment shown in FIG. 21 have the same reference numerals.
  • This embodiment has the same circuit topology as the ninth, but the first active element is an N-MOSFET 61, the second active element is a P-MOSFET 41, V SS is applied to the first power-supply terminal 31, and V DD is applied to the second power-supply terminal 32.
  • Diode 72 is accordingly connected in the reverse direction: its anode is coupled to the first power-supply terminal 31, and its cathode to the gate of P-MOSFET 62.
  • the operation of the tenth embodiment is illustrated in FIG. 25 for the case of a slow-rising power supply, and in FIG. 26 for the case of a fast-rising power supply, the rise of the power supply being depicted in both cases as a fall of V SS .
  • the waveforms are the same as in FIGS. 22 and 23, with positive and negative reversed. A detailed description will be omitted, since the operation of the tenth embodiment is exactly analogous to the operation of the ninth.
  • the tenth embodiment provides thesame effects for an active-low reset signal as the ninth embodiment provides for an active-high reset signal.
  • FIG. 27 is a circuit diagram of an auto-reset circuit illustrating an eleventh embodiment of the invention. Elements identical to elements of the ninth embodiment shown in FIG. 21 have the same reference numerals.
  • a resistor 53 is coupled between the drain of P-MOSFET 41 and the point of interconnection of resistors 51 and 54, as in the seventh embodiment, and a diode 72 is coupled between the gate of N-MOSFET42 and the first power-supply terminal 31, as in the ninth embodiment.
  • FIG. 28 is a voltage waveform diagram illustrating the operation of the eleventh embodiment when V DD rises rapidly in relation to the time constant of resistors 53 and 54 and capacitor 71.
  • the waveforms in intervals A through E at power-up are substantially the same as the corresponding waveforms of the seventh embodiment, as illustrated in FIG. 16.
  • the waveforms during the momentary power interruption and its recoveryin intervals J through R are generally similar to the corresponding waveforms of the ninth embodiment, as illustrated in FIG. 22, but since V G has a lower steady-state value, interval J, during which diode 72 is non-conducting, is longer and interval K, during which diode 72 conducts and MOSFETS 41 and 42 are both still on, is shorter.
  • capacitor 71 has less time to discharge through diode 72 during intervals K, L, and M than in FIG. 22, the discharge starts from a lower steady-state V G potential, so V G arrives at approximately the same value at the end of interval M in both FIGS. 28 and 22, and falls to about the same value in intervals N and O. This value is low enough to turn off N-MOSFET 42 and create a reset signal in intervals O and P that is substantially the same as the one in intervals B and C at power-up.
  • FIG. 29 illustrates the operation of the eleventh embodiment when V DD rises quickly in relation the time constant of resistors 53 and 54 and capacitor 71.
  • the waveforms are similar to those of the ninth embodiment in FIG. 23, except that the steady-state V G potential is lower, as inthe seventh embodiment.
  • V DD rises from the V SS level to the steady state during intervals O and U
  • V G rises from a value slightly higher than V SS to the threshold value V TN of N-MOSFET 42 in interval U.
  • a reset signal is therefore output during intervals O and U.
  • the eleventh embodiment combines the effects of the seventh and ninth embodiments: the release level of the reset signal can be altered by changing the resistance ratio of resistors 51 and 53; owing to resistor 54and capacitor 71, a reset signal is output even if the power supply rises quickly; and due to diode 72, capacitor 71 can discharge quickly during a momentary power interruption, so that a reset signal can be output again when power is recovered.
  • FIG. 30 is a circuit diagram of an auto-reset circuit illustrating a twelfth embodiment of the invention. Elements identical to elements of thetenth and eleventh embodiments shown in FIGS. 24 and 27 have the same reference numerals.
  • This embodiment has the same circuit topology as the eleventh, but the first active element is an N-MOSFET 61, the second active element is a P-MOSFET 41, V SS is applied to the first power-supply terminal 31, and V DD is applied to the second power-supply terminal 32.
  • Diode 72 is connected so that its anode is coupled to the first power-supply terminal 31 and its cathode to the gate of P-MOSFET 62.
  • the operation of the twelfth embodiment is illustrated in FIG. 31 for the case of a slow-rising power supply and in FIG. 32 for the case of a fast-rising power supply, the rise of the power supply being depicted as afall of V SS .
  • the waveforms are the same as in FIGS. 28 and 29 but withpositive and negative reversed. A detailed description will be omitted, theoperation of the twelfth embodiment being analogous to the operation of theeleventh.
  • the twelfth embodiment provides the same effects for an active-low reset signal as are provided for an active-high reset signal bythe eleventh embodiment.
  • FIG. 33 is a circuit diagram of an auto-reset circuit illustrating a thirteenth embodiment of the invention. Elements identical to elements of the first embodiment shown in FIG. 1 have the same reference numerals.
  • the gate (third terminal) of the P-MOSFET 41 shown in FIG. 1 is coupled to a control signal input terminal 81 which receives a control signal CS1, and output terminal 33 is coupled to the first input terminal of a two-input AND gate 91.
  • the second input terminalof the AND gate 91 is coupled to another control signal input terminal 82, which receives a control signal CS2.
  • the output side of AND gate 91 is coupled to an output terminal 83.
  • the reset signal RS is the signal outputfrom output terminal 83; that is, the reset signal RS is gated by AND gate 91.
  • control signal CS1 is held low and control signal CS2 is held high.
  • the gate potential of P-MOSFET 41 is therefore V SS as in FIG. 1, and the outputs at output terminals 33 and 83 are either both high or both low.
  • This circuit accordingly operates in substantially the same way as the first embodiment.
  • control signal CS1 is driven high and control signal CS2 low.
  • the gate and source of P-MOSFET 41 are now both at the V DD level, so P-MOSFET 41 turns off.
  • the gate potential of N-MOSFET 42 is then pulled down through resistor 51 to V SS , so N-MOSFET 42 also turns off. Accordingly, no current flows through the auto-reset circuit.
  • Output terminal 33 is pulled up through resistor 52 to the V DD level, but since control signal CS2 is low, the reset signal RS output at output terminal 83 remains low.
  • Another useful possibility is to route the signal from output terminal 33 to some circuits in an LSI or other device, and the signal from output terminal 83 to other circuits. Static current consumption can then be measured in either a partially or a completely initialized state.
  • AND gate 91 can be eliminated and the reset signal RS taken directly from output terminal 33.
  • the advantage of performing static current tests with current flow through the auto-reset circuit cut off is that it removes the ambiguity resulting from inexact knowledge of the size of that current. That is, it improves the resolution of the tests, enabling more accurate identification of devices with photolithography defects or other defects that might impair long-term reliability.
  • FIG. 34 is a circuit diagram of an auto-reset circuit illustrating a fourteenth embodiment of the invention. Elements identical to elements of the second embodiment shown in FIG. 3 have the same reference numerals.
  • the gate of N-MOSFET 61 is coupled to a control signal input terminal 81, and output terminal 33 is coupled to the first input terminal of a two-output OR gate 92.
  • the second input terminal of the OR gate 92 is coupled to another control signal input terminal 82 and the output side of OR gate 92 is coupled to an output terminal 83.
  • the inputs at control signal input terminals 81 and82 are control signals CS1 and CS2, and the reset signal RS, which is active low, is taken from output terminal 83; that is, the reset signal RSis gated by OR gate 92.
  • control signal CS1 is high and control signal CS2 is low, and this embodiment operates like the second embodiment.
  • control signal CS1 is driven low to turn off N-MOSFET 61.
  • the gate potential V G of P-MOSFET 62 is then pulled up to V DD through resistor 51, so P-MOSFET 62 also turns off and currentflow through the auto-reset circuit ceases.
  • control signal CS2 is left low, permitting output of a low reset signal RS from output terminal 83; otherwise, control signal CS2 is driven high, forcing RS to remain inactive (high).
  • This embodiment has the same effect as the thirteenth embodiment, the only difference being that the meanings of the high and low levels of the resetand control signals are reversed.
  • FIG. 35 is a circuit diagram of an auto-reset circuit illustrating a fifteenth embodiment of the invention. Elements identical to elements of the third embodiment shown in FIG. 5 have the same reference numerals.
  • the gate of P-MOSFET 41 is coupled to a control signal input terminal 81 which receives a control signal CS1.
  • Control signal CS1 is driven low during normal operation and high during static current measurements. If it is necessary to prevent output of a reset signal during such measurements, an AND gate can be coupled to output terminal 33 as in the thirteenth embodiment. This embodiment combines features of the third and thirteenth embodiments, enabling current flow through the auto-reset circuit to be reduced to zero for testpurposes.
  • FIG. 36 is a circuit diagram of an auto-reset circuit illustrating a sixteenth embodiment of the invention. Elements identical to elements of the fourth embodiment shown in FIG. 7 have the same reference numerals.
  • the gate of N-MOSFET 61 is coupled to a control signal input terminal 81 that receives a control signal CS1.
  • Control signal CS1 is driven high during normal operation and low during static current measurements. If it is necessary to prevent output of a reset signal during such measurements, an OR gate can be coupled to outputterminal 33 as in the fourteenth embodiment. Like the fourteenth embodiment, the sixteenth embodiment enables current flow through the auto-reset circuit to be reduced to zero during the measurement.
  • FIG. 37 is a circuit diagram of an auto-reset circuit illustrating a seventeenth embodiment of the invention. Elements identical to elements ofthe fifth embodiment shown in FIG. 9 have the same reference numerals.
  • This embodiment has three three-terminal active elements, the first and second being the P-MOSFET 41 and N-MOSFET 42 shown in FIG. 9, and the third being another N-MOSFET 43.
  • the gates of P-MOSFET 41 and N-MOSFET 43 are both coupled to a control signal input terminal 81 that receives a control signal CS1.
  • the drain of N-MOSFET 43 is coupled to the gate of N-MOSFET 42.
  • the source of N-MOSFET 43 is coupled to the second power-supply terminal 32.
  • control signal CS1 is held low, turning off N-MOSFET 43 and allowing P-MOSFET 41 to turn on when V DD rises.
  • the circuit accordingly operates as did the fifth embodiment illustrated in FIG. 9.
  • control signal CS1 is driven high, turning P-MOSFET 41 off and N-MOSFET 43 on.
  • Capacitor 71 and the gate of N-MOSFET 42 are coupled through N-MOSFET 43 to the second power-supply terminal 32, so capacitor 71 rapidly discharges and the gate potential V G of N-MOSFET 42 drops to the V SS level, turning N-MOSFET 42 off. With P-MOSFET 41 and N-MOSFET 42 off and capacitor 71 discharged, no current flows and accurate static current measurements can be carried out.
  • FIG. 38 is a circuit diagram of an auto-reset circuit illustrating an eighteenth embodiment of the invention. Elements identical to elements of the sixth and seventeenth embodiments shown in FIGS. 12 and 37 have the same reference numerals.
  • This embodiment has the same circuit topology as the seventeenth embodiment, but the first active element is an N-MOSFET 61, the second active element is a P-MOSFET 62, the third active element is a P-MOSFET 63, V SS is input to the first power-supply terminal 31, and V DD is input to the second power-supply terminal 32.
  • Control signal CS1 is driven high during normal operation and low during static current measurements.
  • FIG. 39 is a circuit diagram of an auto-reset circuit illustrating a nineteenth embodiment of the invention. Elements identical to elements of the seventh and seventeenth embodiments shown in FIGS. 15 and 37 have the same reference numerals.
  • this embodiment operates like the seventh embodiment, as shown in FIGS. 16 and 17.
  • control signal CS1 is driven high, P-MOSFET 41 turns off, N-MOSFET 43 turns on, capacitor 71 discharges, and N-MOSFET 42 turns off, cutting off current flow as in the seventeenth embodiment and permitting static current consumption to be measured accurately.
  • an ANDgate can be coupled to output terminal 33 as in the thirteenth embodiment, to control reset signal output during the measurement.
  • FIG. 40 is a circuit diagram of an auto-reset circuit illustrating a twentieth embodiment of the invention. Elements identical to elements of the eighth and eighteenth embodiments shown in FIGS. 18 and 38 have the same reference numerals.
  • this embodiment When a high control signal CS1 is input at control signal input terminal 81, this embodiment operates like the eighth embodiment, as shown in FIGS.19 and 20.
  • control signal CS1 When control signal CS1 is driven low, N-MOSFET 61 turns off, P-MOSFET 63 turns on, capacitor 71 discharges, and P-MOSFET 62 turns off, cutting off current flow as in the eighteenth embodiment and permitting static current to be measured accurately.
  • an OR gate can be coupled to output terminal 33 as in the fourteenth embodiment, to control reset signal output during the measurement.
  • FIG. 41 is a circuit diagram of an auto-reset circuit illustrating a twenty-first embodiment of the invention. Elements identical to elements of the ninth and seventeenth embodiments shown in FIGS. 21 and 37 have thesame reference numerals.
  • this embodiment operates like the ninth embodiment, as shown in FIGS. 22 and 23.
  • control signal CS1 is driven high, P-MOSFET 41 turns off, N-MOSFET 43 turns on, capacitor 71 discharges, and N-MOSFET 42 turns off, cutting off current flow as in the seventeenth embodiment and permitting static current to be measured accurately.
  • an AND gate can becoupled to output terminal 33 as in the thirteenth embodiment, to control reset signal output during the measurement.
  • FIG. 42 is a circuit diagram of an auto-reset circuit illustrating a twenty-second embodiment of the invention. Elements identical to elements of the tenth and eighteenth embodiments shown in FIGS. 24 and 38 have the same reference numerals.
  • control signal CS1 When a high control signal CS1 is input at control signal input terminal 81, this embodiment operates like the tenth embodiment, as shown in FIGS. 25 and 26.
  • control signal CS1 When control signal CS1 is driven high, N-MOSFET 61 turns off, P-MOSFET 63 turns on, capacitor 71 discharges, and P-MOSFET 62 turns off, cutting off current flow as in the eighteenth embodiment and permitting static current to be measured accurately.
  • an OR gate can be coupled to output terminal 33 as in the fourteenth embodiment, to control reset signal output during the measurement.
  • FIG. 43 is a circuit diagram of an auto-reset circuit illustrating a twenty-third embodiment of the invention. Elements identical to elements of the eleventh and seventeenth embodiments shown in FIGS. 27 and 37 have the same reference numerals.
  • control signal input terminal 81 When a low control signal CS1 is input at control signal input terminal 81, this embodiment operates like the eleventh embodiment, as shown in FIGS. 28and 29.
  • control signal input terminal 81 is driven high, P-MOSFET 41 turns off, N-MOSFET 43 turns on, capacitor 71 discharges, and N-MOSFET 42 turns off, cutting off current flow as in the seventeenth embodiment and permitting static current to be measured accurately.
  • an AND gate can be coupled to output terminal 33 as in the thirteenth embodiment,to control reset signal output during the measurement.
  • FIG. 44 is a circuit diagram of an auto-reset circuit illustrating a twenty-fourth embodiment of the invention. Elements identical to elements of the twelfth and eighteenth embodiments shown in FIGS. 30 and 38 have the same reference numerals.
  • control signal input terminal 81 When a high control signal CS1 is input at control signal input terminal 81, this embodiment operates like the twelfth embodiment, as shown in FIGS. 31 and 32.
  • control signal input terminal 81 is driven high, N-MOSFET 61 turns off, P-MOSFET 63 turns on, capacitor 71 discharges, and P-MOSFET 62 turns off, cutting off current flow as in the eighteenth embodiment and permitting static current to be measured accurately.
  • an OR gate can be coupled to output terminal 33 as in the fourteenth embodiment, to control reset signal output during the measurement.
  • a basic feature of the preceding embodiments has been that the gate of the first active element is coupled to the second power-supply terminal 32, asshown in the first and second embodiments.
  • the third through twenty-fourth embodiments have shown various features in addition to this basic feature. The remaining embodiments will show how these additional features can also be applied when the gate of the first active element is connected to its drain, and will describe certain waveforms associated with these embodiments in more detail.
  • FIG. 45 is a circuit diagram of an auto-reset circuit illustrating a twenty-fifth embodiment of the invention. Elements identical to elements of the fifth embodiment shown in FIG. 9 have the same reference numerals.
  • This embodiment differs from the fifth in that the gate and drain of P-MOSFET 41 are mutually interconnected, instead of the gate being coupledto the second power-supply terminal 32 as in FIG. 9.
  • P-MOSFET 41 therefore operates as a so-called PMOS diode, conducting in only one direction.
  • FIG. 46 is a voltage waveform diagram illustrating the case in which V DD rises slowly in relation to the time constant of resistor 54 and capacitor 71.
  • the threshold voltages V TP and V TN of the P-MOSFET41 and N-MOSFET 42 are shown as being equal, but this is not a restriction.This embodiment remains applicable when V TP and V TN differ as, for example, in FIG. 10.
  • V DD -V SS exceeds the threshold voltage V TP of P-MOSFET 41 and P-MOSFET 41 turns on. Since its gate and drainare interconnected, however, P-MOSFET does not turn on hard. If the resistance of resistor 51 is sufficiently high, the gate-source voltage ofP-MOSFET 41, which equals the voltage drop across P-MOSFET 41, stays near V TP . The drain and gate potentials of MOSFET 41 follow the rise of V DD , staying substantially equal to V DD -V TP . This potential is provided through resistor 54 to capacitor 71 and the gate of N-MOSFET 42, causing the gate potential V G of N-MOSFET 42 also to rise.
  • V G stays substantially equal to V DD -V TP , rising parallel to V DD as shown in FIG. 46.
  • V G -V SS is below the threshold voltage V TN of N-MOSFET 42, N-MOSFET 42 remains off and the output voltage V O continues to rise together with V DD .
  • interval D when V DD increases further, V G -V SS exceeds V TN , so N-MOSFET 42 turns on and the output voltage V O at the output terminal 33 reverts to the V SS level. This state is maintainedin interval E.
  • V DD is at its steady-state value
  • V G holds constant at about V DD -V TP
  • N-MOSFET 42 remains on
  • the reset signal remains at the V SS level.
  • the steady-state supply voltage V DD -V SS should be high enough toassure that N-MOSFET 42 will turn on hard when its gate potential is V G is equal to V DD -V TP . If that condition is satisfied, the operation depicted in FIG. 46 is essentially the same as the operationof the fifth embodiment shown in FIG. 10.
  • FIG. 47 is a voltage waveform diagram illustrating the case in which V DD rises rapidly in relation to the time constant of resistor 54 andcapacitor 71. Again the threshold voltages V TP and V TN of P-MOSFET 41 and N-MOSFET 42 are shown as equal.
  • V DD rises quickly to its steady-state value.
  • V G rises at a slower rate controlled by the time constant of resistor 54 and capacitor 71, and V G -V SS does not reach the threshold voltage V TN of N-MOSFET 42 until the end of interval H, when V DD has already attained its steady state.
  • a reset signal is output during intervals G and H.
  • V G -V SS exceeds V TN , so N-MOSFET turns on and the reset signal RS returns to the V SS level, while V G continues to rise to its steady-state value of V DD -V TP .
  • V O of the reset signal RS has been described asrising together with V DD
  • the actual waveform depends on the capacitive load coupled to output terminal 33. Circuit constants should beselected so that this load has time to charge adequately before V G -V SS reaches V TN .
  • the capacitive load is 0.5 picofarads
  • the resistances of resistors 51, 52, and 54 are 500 kilohms
  • the threshold voltages V TP and V TN are 0.7 V
  • the supply voltage rises to a steady state of 5 V in a few hundred nanoseconds
  • a capacitance of about 3 picofarads for capacitor 71 should provide a usable reset signal.
  • FIG. 48 is a circuit diagram of an auto-reset circuit illustrating a twenty-sixth embodiment of the invention. Elements identical to elements of the sixth embodiment shown in FIG. 12 have the same reference numerals.
  • the twenty-sixth embodiment has the same circuit topology as the twenty-fifth, with the gate and drain of the first active element interconnected, but that first active element is now an N-MOSFET 61, while the second active element is a P-MOSFET 62, and V SS is applied to the first power-supply terminal 31, while V DD is applied to the second power-supply terminal 32.
  • FIG. 49 The operation of the twenty-sixth embodiment is illustrated in FIG. 49 for the case of a slowly-rising power supply, and in FIG. 50 for the case of aquickly-rising power supply, the rise of the power supply in both cases being shown as a fall of V SS .
  • the operation is analogous to the operation of the twenty-fifth embodiment as shown in FIGS. 46 and 47, withpositive and negative reversed, so a detailed description will be omitted.
  • FIG. 51 illustrates this behavior for the twenty-fifth embodiment with a fast-rising power supply.
  • FIG. 52 illustrates this behavior for the twenty-sixth embodiment, also with a fast-rising power supply.
  • interval I capacitor 71 charges to a steady-state potential V G of V DD -V TP as discussed above.
  • V DD In interval Q, at the onset of the power interruption V DD begins to fall.
  • the drain voltage of P-MOSFET 41 also begins to fall, allowing capacitor 71 to start discharging through resistor 54, thence through resistor 51 to the V SS level at the second power-supply terminal 32.
  • V DD falls at the same rate at which it rose, this ratebeing rapid in comparison with the time constant of resistor 54 and capacitor 71.
  • capacitor 71 is barely able to discharge at all and the gate potential of P-MOSFET 41 is held up by the charge in capacitor 71.
  • the gate potential of P-MOSFET 41 becomes equal to or higher than both the source and drain potentials of P-MOSFET 41, which accordingly turns off.
  • Capacitor 71 is thereby prevented from discharging through P-MOSFET 41; it can discharge only through resistors 54 and 51 to terminal 32, which is at the V SS level. This discharge continues after V DD has dropped to the V SS level, in interval S in FIG. 51.
  • the gate potential of N-MOSFET 42 must be reduced at least to 0.7 V. If resistors 54 and 51 have resistances of 500 kilohms, the threshold voltage V TP of P-MOSFET 41 is 0.7 V, the steady-state V DD and V SS values are5 V and 0 V, respectively, and capacitor 71 has a capacitance of 3 picofarads, then it takes capacitor 71 approximately 5.4 microseconds to discharge from its steady-state value of 4.3 V to 0.7 V. To produce a dependable rest signal, the gate potential V G of N-MOSFET 42 must be reduced to an even lower value such as 0.2 V, but this takes still longer:approximately 9.2 microseconds.
  • FIG. 52 which shows the behavior of the twenty-sixth embodiment in a momentary power interruption, is analogous to FIG. 51 with positive and negative reversed, so a detailed description will be omitted.
  • no reset signal is output at all for a power interruption on the order of one microsecond, and with the circuit constants mentioned above, output ofa reset signal remains undependable for power interruptions lasting up to about 9.2 microseconds.
  • FIG. 53 is a circuit diagram of an auto-reset circuit illustrating a twenty-seventh embodiment of the invention. Elements identical to elementsof the ninth embodiment shown in FIG. 21 have the same reference numerals. This embodiment has the same circuit topology as the ninth, except that the gate and drain of P-MOSFET 41 are interconnected as in the twenty-fifth embodiment.
  • FIG. 54 is a voltage waveform diagram illustrating the operation of the twenty-seventh embodiment with a slowly-rising power supply.
  • the waveformsin intervals A through E are substantially the same as the waveforms of thetwenty-fifth embodiment illustrated in FIG. 46.
  • V DD falls at the same rate at which it rose, the rate being controlled by a time constant of thepower supply. If the fall occurs over a period of several tens of milliseconds, for example, and resistors 51 and 54 have resistances of 500kilohms while capacitor 71 has a capacitance of 3 picofarads (giving them atime constant of 3 microseconds), then capacitor 71 is able to discharge ata substantially matching rate, so the gate potential V G of N-MOSFET 42and the gate and drain potentials of P-MOSFET 41 all remain substantially equal to V DD -V TP . Diode 72 remains in the reverse-biased, hencenon-conducting, state.
  • V G -V SS becomes less than the thresholdvoltage V TN of N-MOSFET 42, which accordingly turns off, and the output voltage V O at output terminal 33 is pulled up through resistor52 to V DD .
  • resistor 52 has a value of 500 kilohms, and the V DD level at this time is 1.4 V, for example, then V 0 rises to 1.2 V in about 486 nanoseconds.
  • V DD After remaining at the V SS level in interval M, V DD begins to rise again, and the same operations take place in intervals N, O, and P asoccurred in intervals B, C, and D at power-up.
  • a reset signal is generated at both ends of the power interruption: when power is lost in intervals K and L, and when power is regained in intervals N and O.
  • the waveforms in intervals A, G, H, and I in FIG. 55 are substantially the same as in FIG. 47, which illustrates the twenty-fifth embodiment.
  • V DD falls from itssteady state to a value equal to the potential of capacitor 71 minus the threshold voltage of diode 72.
  • This voltage drop affects the drain voltageof P-MOSFET 41 and allows capacitor 71 to discharge through resistor 54, but the interval is too brief for significant discharge to occur.
  • the resistance of resistors 51 and 54 is 500 kilohms
  • the capacitance of capacitor 71 is 3 picofarads
  • the threshold voltages of P-MOSFET 41 and diode 72 are 0.7 V
  • V DD falls from a steady-state level of 5.0 V,for example, interval Q is too short for the discharge of capacitor 71 to be noticeable in the drawing.
  • Capacitor 71 remains charged to a potential of substantially 4.3 V.
  • interval S the forward voltage across diode 72 is insufficient (less than 0.7 V) for substantial current flow, but the discharge of capacitor 71 continues at a more moderate rate through resistors 54 and 51. Since capacitor 71 has already discharged to 0.7 V in interval R, it is able to discharge fully to the V SS level in interval S.
  • V DD rises again in interval U and the same process takes place in intervals T, U, V, and Was occurred in intervals A, G, H, and I at power-up, resulting in reliable output of a reset signal in intervals U and V.
  • V G It is not necessary for V G to fall all the way to the V SS level in order for a reset signal to be output; it suffices for V G to be reduced to about 0.2 V.
  • capacitor 71 can discharge through resistors 54 and 51 from 0.7 V to 0.2 Vin about 3.8 microseconds, enabling a dependable reset signal to be output after a power interruption of that duration, whereas in the twenty-fifth embodiment the necessary duration was approximately 9.2 microseconds.
  • FIG. 56 is a circuit diagram of an auto-reset circuit illustrating a twenty-eighth of the invention. Elements identical to elements of the tenth embodiment shown in FIG. 24 have the same reference numerals. Although drawn differently, this auto-reset circuit has the same topology as FIG. 24, except that the gate and drain of N-MOSFET 41 are interconnected as in the twenty-sixth embodiment.
  • FIGS. 57 and 58 illustrate the operation of the twenty-eighth embodiment with slow-rising and fast-rising power supplies. A detailed description will be omitted since the operation is exactly analogous to FIGS. 54 and 55 with positive and negative reversed.
  • a reliable reset signal is output after a momentary power interruption lasting, for example, as little as 3.8 microseconds.
  • FIG. 59 is a circuit diagram of an auto-reset circuit illustrating a twenty-ninth embodiment of the invention. Elements identical to elements of the twenty-seventh embodiment shown in FIG. 53 have the same reference numerals.
  • This embodiment provides a control signal input terminal 81 for stopping current flow through the auto-reset circuit during static currentmeasurements, as in the thirteenth to twenty-fourth embodiments.
  • a third three-terminal active element is connected in series with the first.
  • the third three-terminal active element is a P-MOSFET 44, which is coupled in series between the gate and drain of the P-MOSFET 41, and also in series between the drain of P-MOSFET 41 and resistors 51 and 54.
  • the source of P-MOSFET 44 is coupled tothe drain of P-MOSFET 41
  • the drain of P-MOSFET 44 is coupled both to the gate of P-MOSFET 41 and to a point between resistors 51 and 54.
  • the gate of P-MOSFET 44 is coupled to control signal input terminal 81, at which a control signal CS1 is input.
  • P-MOSFET 44 is formed in the same substrate or well as P-MOSFET 41, which is biased to the V DD level asindicated in the drawing.
  • control signal CS1 If control signal CS1 is low, then P-MOSFETs 41 and 44 begin to turn on at almost the same time, and P-MOSFET 44 turns on hard in the steady state.
  • the circuit operates substantially as shown in FIGS. 54 and 55, as if P-MOSFET 44 were not present, diode 72 enabling capacitor 71 to discharge and a reset signal to be output after even a brief power interruption.
  • N-MOSFET 42 turns off, and the output voltage V O at output terminal 33 is now pulled up through resistor 52 to the V DD level, resulting in output of a reset signal. Since P-MOSFET 44 and N-MOSFET 42 are turned off, current completely ceases to flow through the auto-reset circuit, permitting accurate measurement of static current consumption in the reset state.
  • FIG. 61 is a circuit diagram of an auto-reset circuit illustrating a thirtieth embodiment of the invention. Elements identical to elements of the twenty-ninth embodiment shown in FIG. 59 have the same reference numerals.
  • the first input terminal of a two-input AND gate 91 is coupled to the output terminal 33, as in the thirteenth embodiment shown in FIG. 33.
  • the second input terminal of AND gate 91 is coupled through aninverter 93 to control signal input terminal 81.
  • the output side of AND gate 91 is coupled to an output terminal 83 for output of the reset signalRS.
  • this embodiment is identical to the operation of the twenty-ninth embodiment except that when control signal CS1 goes high, inverter 93 supplies a low input to AND gate 91, preventingoutput of a reset signal from output terminal 83.
  • a reset signal is output only in interval D after CS1 goes low again, and lasts only until V G -V SS regains the V TN level and N-MOSFET 42 turns on.
  • the pulse width of this reset signal RS is determined by the time constant of resistor 54 and capacitor 71.
  • the thirtieth embodiment enables static current consumption to be measured accurately without output of a reset signal during interval C. After the measurement, when CS1 is driven low again, a further check of circuit operation can be made by confirming that the reset signal RS is output normally in interval D.
  • FIG. 63 is a circuit diagram of an auto-reset circuit illustrating a thirty-first embodiment of the invention. Elements identical to elements of the thirtieth embodiment shown in FIG. 61 have the same reference numerals.
  • This embodiment is the same as the thirtieth except that the inverter 93 ofFIG. 61 is not present and the second input terminal of AND gate 91 is connected to a second control signal input terminal 82.
  • the control signals input at terminals 81 and 82 are designated CS1 and CS2, respectively.
  • control signal CS1 is driven high and control signal CS2 is driven low in intervals B and C.
  • control signal CS1 is returned to the low level, then after a suitable delay spanning intervals D and E, control signal CS2 is returned to the high level.
  • Control signal CS1 turns off P-MOSFET 44 in intervals B and C and N-MOSFET 42 in interval C, reducing current flow to zero.
  • Control signal CS2 forcesthe output of AND gate 91 low and suppresses output of a reset signal during intervals B, C, D, and E. Static current consumption can thus be measured accurately and without output of any reset signal, either during or after the measurement, enabling the device under test to resume operating from the state preceding the measurement.
  • FIG. 65 is a circuit diagram of an auto-reset circuit illustrating a thirty-second embodiment of the invention. Elements identical to elements of the twenty-ninth embodiment shown in FIG. 59 have the same reference numerals.
  • This embodiment has the same circuit topology as the twenty-ninth except that the gate of P-MOSFET 41 is now coupled directly to the drain of P-MOSFET 41, and the gate and drain of P-MOSFET 41 are both coupled to thesource of P-MOSFET 44.
  • This embodiment operates in substantially the same way as the twenty-ninth.
  • control signal CS1 When control signal CS1 is low, P-MOSFET 44 turns on and the circuit is functionally the same as the circuit of FIG. 53, which illustrates the twenty-seventh embodiment.
  • CS1 When CS1 is high, P-MOSFET 44 turns off, capacitor 71 discharges, N-MOSFET 42 turns off, and current flow is reduced to zero as in the twenty-ninth embodiment.
  • FIG. 66 is a circuit diagram of an auto-reset circuit illustrating a thirty-third embodiment of the invention. Elements identical to elements of the twenty-ninth embodiment shown in FIG. 59 have the same reference numerals.
  • P-MOSFET 44 is now coupled in series between the first power-supply terminal 31 and the source of P-MOSFET 41.
  • the first power-supply terminal31 is connected to the source of P-MOSFET 44
  • the drain of P-MOSFET 44 is coupled to the source of P-MOSFET 41
  • the gate of P-MOSFET 44 is coupled to control signal input terminal 81.
  • the gate and drain of P-MOSFET 41 are mutually interconnected, and are coupled to a point between resistors 51 and 54.
  • This embodiment operates in the same way as the twenty-ninth and thirty-second, current flow being cut off when control signal CS1 is high.When CS1 is low the circuit operates normally, as in the twenty-seventh embodiment.
  • FIG. 67 is a circuit diagram of an auto-reset circuit illustrating a thirty-fourth embodiment of the invention. Elements identical to elements of the twenty-eighth embodiment shown in FIG. 56 have the same reference numerals.
  • This embodiment is identical to the twenty-ninth with the replacement of P-MOSFET 41 by N-MOSFET 61, P-MOSFET 44 by N-MOSFET 64, and N-MOSFET 42 byP-MOSFET 62. Also, V SS is applied to the first power-supply terminal 31, V DD is applied to the second power-supply terminal 32, and the direction of diode 72 is reversed.
  • Control signal CS1 low is normally high, but is driven low to cut off current flow for static current measurements.
  • FIG. 69 is a circuit diagram of an auto-reset circuit illustrating a thirty-fifth embodiment of the invention. Elements identical to elements of the thirty-fourth embodiment shown in FIG. 67 have the same reference numerals.
  • This embodiment is identical to the thirtieth with the replacement of P-MOSFET 41 by N-MOSFET 61, P-MOSFET 44 by N-MOSFET 64, N-MOSFET 42 by P-MOSFET 62, and AND gate 91 by OR gate 92. Also, V SS is applied to the first power-supply terminal 31, V DD is applied to the second power-supply terminal 32, and the direction of diode 72 is reversed.
  • Control signal CS1 is normally high, but is driven low to cut off current flow for measurements of static current consumption.
  • Inverter 93 and OR gate 92 prevent output of a reset signal in interval C.
  • FIG. 71 is a circuit diagram of an auto-reset circuit illustrating a thirty-sixth embodiment of the invention. Elements identical to elements of the thirty-fourth embodiment shown in FIG. 67 have the same reference numerals.
  • This embodiment is the same as the thirty-first with the replacement, again, of P-MOSFET 41 by N-MOSFET 61, P-MOSFET 44 by N-MOSFET 64, N-MOSFET42 by P-MOSFET 62, and AND gate 91 by OR gate 92. Also, V SS is appliedto the first power-supply terminal 31, V DD is applied to the second power-supply terminal 32, and the direction of diode 72 is reversed.
  • control signal CS1 is high andcontrol signal CS2 low.
  • control signal CS2 is driven low and control signal CS2 high.
  • first control signal CS1 is driven high, then control signal CS2 is driven low, preventing output of a reset signal either during or after the measurement.
  • FIG. 73 is a circuit diagram of an auto-reset circuit illustrating a thirty-seventh embodiment of the invention. Elements identical to elementsof the thirty-fourth embodiment shown in FIG. 67 have the same reference numerals.
  • FIG. 74 is a circuit diagram of an auto-reset circuit illustrating a thirty-eighth embodiment of the invention. Elements identical to elements of the thirty-seventh embodiment shown in FIG. 73 have the same reference numerals.
  • N-MOSFET 64 is coupled in series between the first power-supply terminal 31 and the source of N-MOSFET 61. As explained in the thirty-third embodiment this change also does not affect the operationof the circuit, a description of which will therefore be omitted.
  • the twenty-ninth to thirty-eighth embodiments enable current flow to be stopped for measurement purposes by applying a control signal CS1. However, current flow does not stop immediately when the control signal isapplied; there is a delay, as shown in interval B in FIGS. 60, 62, 64, 68, 70, and 72, before capacitor 71 can discharge to the threshold voltage of N-MOSFET 42 or P-MOSFET 62. If capacitor 71 has a capacitance of 3 picofarads and resistors 51 and 54 a resistance of 500 kilohms each, and the steady-state supply voltage is five volts, then the delay is about 5.4microseconds.
  • the delay is on the order of a few microseconds to a few tens of microseconds. Since automatic test equipment may operate at megahertz rates or faster, this delay is not insignificant.
  • the delay can be eliminated by means of a fourth three-terminal active element, as will be shown in the thirty-ninth to forty-fourth embodiments.
  • FIG. 75 is a circuit diagram of an auto-reset circuit illustrating a thirty-ninth embodiment of the invention. Elements identical to elements of the twenty-ninth embodiment shown in FIG. 59 have the same reference numerals.
  • the fourth active element is an N-MOSFET 45.
  • the drain of N-MOSFET 45 is coupled to the gate of N-MOSFET 42.
  • the source of N-MOSFET 45 is coupled to power-supply terminal 32, which is at the V SS level, and the well or substrate in which N-MOSFET 45 is formed is also biased to this level.
  • the gate of N-MOSFET 45 is coupled to control signal input terminal 81.
  • control signal CS1 When control signal CS1 is low, P-MOSFET 44 is on and N-MOSFET 45 is off and the circuit becomes equivalent to the twenty-seventh embodiment shown in FIG. 53; that is, it operates as in FIGS. 54 and 55.
  • interval D when control signal CS1 goes low again, P-MOSFET 44 turns onand N-MOSFET 45 turns off. Capacitor 71 now begins to charge through P-MOSFETs 41 and 44 and resistor 54, and the gate potential V G of N-MOSFET 42 begins to rise.
  • V G -V SS exceeds the threshold voltage V TN of N-MOSFET 42, the N-MOSFET 42 turns on and the output voltage V O falls quickly to the V SS level.
  • the gate potential V G continues rising to its steady-state level of V DD -V TP , as shown in interval E.
  • static current consumption can be measuredwithin a few nanoseconds, or a few tens of nanoseconds, of the application of control signal CS1, as compared with 5.4 microseconds, for example, in the twenty-ninth embodiment.
  • FIG. 77 is a circuit diagram of an auto-reset circuit illustrating a fortieth embodiment of the invention. Elements identical to elements of the thirty-second embodiment shown in FIG. 65 have the same reference numerals.
  • the same N-MOSFET 45 as in the thirty-ninth embodiment is coupled to the second power-supply terminal 32, the gate of N-MOSFET 42, and control signal input terminal 81.
  • the same functions and effects are obtained as in the thirty-ninth embodiment.
  • FIG. 78 is a circuit diagram of an auto-reset circuit illustrating a forty-first embodiment of the invention. Elements identical to elements ofthe thirty-third embodiment shown in FIG. 66 have the same reference numerals.
  • an N-MOSFET 45 is coupled to the second power-supply terminal 32, the gate of N-MOSFET 42, and control signal input terminal 81, providing the same functions and effects as in the thirty-ninth embodiment.
  • FIG. 79 is a circuit diagram of an auto-reset circuit illustrating a forty-second embodiment of the invention. Elements identical to elements of the thirty-fourth embodiment shown in FIG. 67 have the same reference numerals.
  • This embodiment is identical to the thirty-ninth with the replacement of P-MOSFETs 41 and 44 by N-MOSFETs 61 and 64, the replacement of N-MOSFETs 42 and 45 by P-MOSFETs 62 and 65, and the reversal of the direction of diode 72.
  • V SS is applied to the first power-supply input terminal 31,and V DD to the second power-supply input terminal 32.
  • Static current measurement can begin within a few nanoseconds, ora few tens of nanoseconds, of the application of control signal CS1.
  • FIG. 81 is a circuit diagram of an auto-reset circuit illustrating a forty-third embodiment of the invention. Elements identical to elements ofthe thirty-seventh embodiment shown in FIG. 73 have the same reference numerals.
  • a P-MOSFET 65 is coupled to the second power-supply terminal 32, the gate of P-MOSFET 62, and control signal input terminal 81, with the same functions and effects as in the forty-second embodiment.
  • FIG. 82 is a circuit diagram of an auto-reset circuit illustrating a forty-fourth embodiment of the invention. Elements identical to elements of the thirty-eighth embodiment shown in FIG. 74 have the same reference numerals.
  • a P-MOSFET 65 is coupled to the second power-supply terminal 32, the gate of P-MOSFET 62, and control signal input terminal 81, providing the same functions and effects as in the forty-second embodiment.
  • resistors 51 and 52, or resistors 51, 52, and 53 have resistance values of about 500 kilohms and the supply voltage is 5 V, total steady-state current flow through the auto-reset circuit is between ten and twenty microamperes. This amount of current is insignificant in comparison with the current drawn by most LSI and other devices during operation.
  • the invention accordingly can provide a reliablereset signal without dissipating excessive current.
  • an AND gate or OR gate can be added to the thirty-ninth through forty-fourth embodiments to suppress output ofa reset signal during static current measurements, as was done in the thirtieth and thirty-fifth embodiments.
  • the three-terminal active elements need not be MOSFETs; other active elements in which conduction between a first terminal and a second terminal is controlled by the input at a thirdterminal can be employed instead.

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US5552736A (en) * 1995-04-19 1996-09-03 Hewlett-Packard Company Power supply detect circuit operable shortly after an on/off cycle of the power supply
US6259285B1 (en) * 1997-12-05 2001-07-10 Intel Corporation Method and apparatus for detecting supply power loss
US20020002672A1 (en) * 2000-06-19 2002-01-03 Alcatel Method of rebooting terminals connected to a local area network and devices for implementing the method
US6650154B2 (en) * 2001-11-28 2003-11-18 Fujitsu Limited Starter circuit
US20060117168A1 (en) * 2004-11-30 2006-06-01 Hon Hai Precision Industry Co., Ltd. Computer system with restart control circuit
US20060284660A1 (en) * 2005-06-17 2006-12-21 Kuan-Hong Hsieh Reset device and display device having same
US20070139988A1 (en) * 2005-12-20 2007-06-21 Stmicroelectronics S.A. Detector of noise peaks in the power supply of an integrated circuit
US20080030220A1 (en) * 2006-08-03 2008-02-07 Agarwal Kanak B Characterization Array and Method for Determining Threshold Voltage Variation
US8531194B2 (en) 2011-03-24 2013-09-10 Freescale Semiconductor, Inc. Selectable threshold reset circuit

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US5942925A (en) * 1997-09-30 1999-08-24 Siemens Aktiengesellschaft Power-on detection and enabling circuit with very fast detection of power-off
EP0986175A1 (fr) * 1998-09-08 2000-03-15 EM Microelectronic-Marin SA Circuit d'initialisation, notamment lors de la mise sous tension
US8111577B2 (en) * 2007-04-17 2012-02-07 Cypress Semiconductor Corporation System comprising a state-monitoring memory element
JP5533156B2 (ja) * 2010-04-06 2014-06-25 セイコーエプソン株式会社 パワーオンリセット回路、集積回路装置及び電子機器
JP6335069B2 (ja) * 2014-08-21 2018-05-30 Ｎｅｃプラットフォームズ株式会社 パワーオンリセット回路
CN105915040A (zh) * 2016-06-08 2016-08-31 无锡思泰迪半导体有限公司 一种漏电电路
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US5436588A (en) * 1993-12-17 1995-07-25 National Semiconductor Corp. Click/pop free bias circuit
US5552736A (en) * 1995-04-19 1996-09-03 Hewlett-Packard Company Power supply detect circuit operable shortly after an on/off cycle of the power supply
US6259285B1 (en) * 1997-12-05 2001-07-10 Intel Corporation Method and apparatus for detecting supply power loss
US20020002672A1 (en) * 2000-06-19 2002-01-03 Alcatel Method of rebooting terminals connected to a local area network and devices for implementing the method
US6954863B2 (en) * 2000-06-19 2005-10-11 Alcatel Local area network terminal adapted to be rebooted with local power supply interruption if remote power supply is not being received
US6650154B2 (en) * 2001-11-28 2003-11-18 Fujitsu Limited Starter circuit
US20060117168A1 (en) * 2004-11-30 2006-06-01 Hon Hai Precision Industry Co., Ltd. Computer system with restart control circuit
US20060284660A1 (en) * 2005-06-17 2006-12-21 Kuan-Hong Hsieh Reset device and display device having same
US20070139988A1 (en) * 2005-12-20 2007-06-21 Stmicroelectronics S.A. Detector of noise peaks in the power supply of an integrated circuit
US7839182B2 (en) * 2005-12-20 2010-11-23 Stmicroelectronics S.A. Detector of noise peaks in the power supply of an integrated circuit
US20080030220A1 (en) * 2006-08-03 2008-02-07 Agarwal Kanak B Characterization Array and Method for Determining Threshold Voltage Variation
US20080129326A1 (en) * 2006-08-03 2008-06-05 International Business Machines Corporation Characterization array circuit
US7423446B2 (en) * 2006-08-03 2008-09-09 International Business Machines Corporation Characterization array and method for determining threshold voltage variation
US20080255792A1 (en) * 2006-08-03 2008-10-16 Agarwal Kanak B Test system and computer program for determining threshold voltage variation using a device array
US20080258750A1 (en) * 2006-08-03 2008-10-23 Agarwal Kanak B Method for determining threshold voltage variation using a device array
US7560951B2 (en) 2006-08-03 2009-07-14 International Business Machines Corporation Characterization array circuit
US7759963B2 (en) 2006-08-03 2010-07-20 International Business Machines Corporation Method for determining threshold voltage variation using a device array
US7917316B2 (en) 2006-08-03 2011-03-29 International Business Machines Corporation Test system and computer program for determining threshold voltage variation using a device array
US8531194B2 (en) 2011-03-24 2013-09-10 Freescale Semiconductor, Inc. Selectable threshold reset circuit

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DE69331420D1 (de) 2002-02-07
EP0802630A3 (en) 1998-02-25
KR100255495B1 (ko) 2000-05-01
DE69330571D1 (de) 2001-09-13
EP0802631B1 (en) 2001-08-29
EP0802630B1 (en) 2002-01-02
KR930018851A (ko) 1993-09-22
EP0802632A2 (en) 1997-10-22
DE69320505T2 (de) 1999-05-06
DE69330689D1 (de) 2001-10-04
EP0802630A2 (en) 1997-10-22
EP0802631A3 (en) 1998-02-25
JPH05259859A (ja) 1993-10-08
EP0802632A3 (en) 1998-03-18
EP0802631A2 (en) 1997-10-22
EP0802632B1 (en) 2001-08-08
DE69320505D1 (de) 1998-10-01
DE69330571T2 (de) 2002-06-27
TW317049B (ko) 1997-10-01
DE69330689T2 (de) 2002-06-20
EP0558042B1 (en) 1998-08-26
DE69331420T2 (de) 2002-08-01
EP0558042A1 (en) 1993-09-01

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